Nasdaq CEO: Promise of the dotcom bubble has now been fulfilled

As bubble talk brews following the 's climb above 5,000, the head of the electronic exchange said this time is different—and the milestone is much more than just a nice round number.

According to Nasdaq CEO Bob Greifeld, the benchmark's climb to a 15-year peak represents the maturity of the "new economy" first ushered in during the days of the dotcom bubble amid the transition from manufacturing to services. Moreover, one key sector could stand out as a leader going forward, he added.

"It means really that you see… the new economy which we talked about 15 years ago has really become the economy," Greifeld said in an interview on CNBC's "Fast Money" this week.

Greifeld said the index acts as a barometer of how the larger economy is doing. "When you look at the Nasdaq composite, these are the companies that have driven our economic growth and are best positioned to drive the economy going forward."

While some on Wall Street have brought up the notion that technology stocks could be reaching bubble levels, Greifeld said that the euphoria of the dotcom boom has transformed into real earnings power built on strong fundamentals.

"You have to look at the earnings multiple first and foremost," Greifeld said. "If we had the same multiple (as 2000) we'd be at Nasdaq 30,000 today, not Nasdaq 5,000," he said. "So it's a different set of circumstances."

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Andreessen Horowitz COO Scott Kupor also said he felt comfortable with tech's current valuation in an interview on CNBC this week. "This feels like the normal course of what we're seeing in terms of technology these days," he said.

Kupor, whose Silicon Valley venture capital firm has investments in companies like Airbnb and Lyft, cited an influx of new players shifting money from public to private markets. According to Kupor, "the hedge funds, the mutual funds, even some of the large tech buyout firms have come into that market."

When asked if the Nasdaq was talking to high profile private companies about potential listings, Greifeld said "If we're not, we're not doing our jobs."

Greifeld said that regarding current listings, biotech is the one sector that could help propel future growth for the Nasdaq. "I would highlight biotech as really being a great story," he said.

The Nasdaq Biotechnology Index has already had an impressive run, climbing more than 30 percent in the past year and 300 percent since 2010.

"With biotech there are about 10,000 diseases that have to be solved, so there's obviously room for growth there," Greifeld said.

"Fast Money" trader Guy Adami agreed. "Biotech is a big component of the Nasdaq now and it wasn't 15 years ago," said Adami, who is also director of advisor advocacy at Private Advisor Group. "I think the names there still work."

Kupor was less willing to pin down a single industry as the future driver. "It will certainly be stuff that neither you nor I have thought about today, that's for sure."